Olefin polymerization catalysts are of great use in industry. Hence, there is interest in finding new catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties.
Catalysts for olefin polymerization are often based on metallocenes as catalyst precursors, which are typically activated either with an alumoxane or with an activator containing a non-coordinating anion. Metallocene catalysts for propylene copolymers, however, have been limited by their inability to produce propylene-ethylene copolymers of high molecular weight or other desired properties. This has been observed for many metallocene structures, such as the syndiospecific Cs symmetric Me2C(Cp)(Flu)ZrCl2, the aspecific C2v symmetric Me2Si(Flu)2ZrCl2, and both the C2 symmetric rac-Me2C(3-iPr-Ind)2ZrCl2 and the fluxional (2-Ph-Ind)2ZrCl2 catalysts for elastomeric polypropylene. This deficit has also been found for the isospecific C2 symmetric rac-Me2Si(2-Me-4,5-Benz-Ind)2ZrCl2 and rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (L. Resconi, C. Fritze, “Metallocene Catalysts for Propylene Polymerization” In Polypropylene Handbook (N. Pasquini, Ed.), Ch. 2.2, Hanser Publishers, Munic 2005). It is thought that, while the 2-Me substitution of this catalyst family suppresses the β-hydrogen transfer to the propylene monomer and thus prevents the formation of low molecular weight polymer, it fails to prevent the β-hydrogen transfer to the ethylene comonomer in case of the latter's presence. This β-hydrogen transfer to the ethylene comonomer becomes the favored chain termination mechanism and leads to the formation of low molecular weight propylene-ethylene copolymers (A. Tynys et al., Macromol. Chem. Phys. 2005, Vol. 206, pp. 1043-1056, “Ethylene-Propylene Copolymerizations: Effect of Metallocene Structure on Termination Reactions and Polymer Microstructure”). Exceptions have been found in some zirconocenes with bulky ligands, such as rac-Me2C(3-tBu-Ind)2ZrCl2, which show a marked increase in molecular weight by ethylene incorporation. This catalyst, however, has shortcomings in terms of homopolymer molecular weight and activity.
Desirable metallocene catalysts for isotactic polypropylene production produce polypropylenes with high melting points. This thought to be due to high stereospecificity and/or regioselectivity in the polymer microstructure. Within the rac-Alk2Si(2-Alk-Ind)2ZrCl2 catalyst family (Alk=Alkyl), the stereospecificity and regioselectivity is continuously being modified. For Example, EP 834 519 A1 relates to rac-Me2Si(2-Me-4-Ar-Ind)2ZrCl2 type metallocenes for the production of rigid, high melting point polypropylenes with high stereoregularity and very low amounts of regio errors. However, these polypropylenes did not fare well under commercially relevant process conditions and suffered from low activity/productivity-levels.
US 2001/0053833 discloses metallocenes where the 2-position is substituted with an unsubstituted heteroaromatic ring or a heteroaromatic ring having at least one substituent bonded to the ring that produce propylene ethylene copolymers having less than desired melting points.
WO 01/058970 relates to impact copolymers having a high melting point and a good rubber content, produced by catalysts of the rac-Me2Si(2-Alk-4-Ar-Ind)2ZrCl2 family when both alkyl substituents were iso-propyl groups. However, these catalysts suffer from activity issues.
WO 02/002576 discloses bridged metallocenes of the (2-Alkyl-4-Ph-Ind)2ZrCl2 family where the 2-positions can be isopropyl and the Ph substituents are substituted in the 3 and 5-positions, particularly with t-butyl. However, these catalysts also suffer from activity/productivity issues at commercial conditions.
WO 03/002583 discloses bridged metallocenes of the (2-Alkyl-4-Ph-Ind)2ZrCl2 family where the 2-positions may be substituted with isopropyl groups and the 4-positions are substituted with Ph group substituted at the 2-position, particularly with a phenyl group. However, these catalysts also suffer from activity/productivity issues at commercial conditions. In addition, these catalysts have relatively low Mw capabilities for isotactic homopolypropylene.
EP 1 250 365; WO 97/40075; and WO 03/045551 relate to bisindenyl metallocenes where substituents at the 2-positions of either of the indenyl ligands are branched or cyclicized in the α-position. However, these catalysts still have relatively limited Mw capabilities for isotactic homopolypropylene.
WO 04/106351 relates to bisindenyl metallocenes having substituents in the 2-positions of the indenyl ligands with the proviso that one ligand is unbranched or bound via a sp2-hybridized carbon atom and the other ligand is branched in the α-position. However, these catalysts still have relatively limited Mw capabilities for isotactic homopolypropylene.
U.S. Pat. No. 8,507,706 discloses bisindenyl metallocenes where at least one 2-position on the indenyl groups is substituted with a group branched at the beta-position and the other 2-position is not branched at the alpha-position. US 2011/0230630 discloses similar metallocenes except that the group at the 2-position is branched in the beta-position and that the beta-carbon atom is a quarternary carbon atom and part of a non-cyclic hydrocarbon system.
U.S. Pat. No. 7,829,495 discloses alkyl substituted metallocenes having a “ . . . C3 or greater hydrocarbyl . . . substitutent bonded to either the LA or LB ring through a primary carbon atom . . . preferably an n-alkyl substituent . . . ” (see column 4, lines 9-12). Further, in the Examples section, (n-propylcyclopentadienyl)(tetramethylcyclopentadienyl)zirconium dichloride combined with methylalumoxane and Davision™ 948 silica is used for ethylene hexene polymerization; bis(n-propyl cyclopentadienyl) zirconium dichloride combined with methylalumoxane and Davision™ 948 silica is used for ethylene hexene polymerization; and dimethylsilyl(flourenyl)(n-propyl cyclopentadienyl) zirconium dichloride combined with methylalumoxane and Davision silica is used for ethylene hexene polymerization.
US 2015/0025208, published Jan. 22, 2015, discloses bridged bisindenyl compounds where the 2-positions on the indene (R2 and R8) are not the same and the 4-positions on the indene (R4 and R10) are substituted phenyl groups, where at least one of R4 and R10 is a phenyl group substituted at the 3 and 5-position.
US 2005/0182266 discloses a process for preparing transition metal compounds having a specific substitution pattern, the corresponding transition metal compounds themselves and their use in the preparation of catalyst systems and also the use of the catalyst systems in the polymerization and copolymerization of olefins.
Other references of interest include: U.S. Pat. Nos. 6,051,727; 6,255,506; EP 0 576 970; U.S. Pat. Nos. 5,459,117; 5,532,396; 5,543,373; 5,585,509; 5,631,202;5,696,045; 5,700,886; 6,492,465; 6,150,481; 5,770,753; 5,786,432; 5,840,644; 6,242,544; 5,869,584; 6,399,533; 6,444,833; 6,559,252; 6,608,224; 6,635,779; 6,841,501; 6,878,786; 6,949,614; 6,953,829; 7,034,173; 7,141,527; 7,314,903; 7,342,078; 7,405,261; 7,452,949; 7,569,651; 7,615,597; 7,799,880; 7,964,679; 7,985,799; 8,222,356; 5,278,264; 5,276,208; 5,049,535; US 2011/0230630; WO 02/002575; WO 02/022575; WO 2003/002583; U.S. Pat. No. 7,122,498; US 2011/0230630; US 2010/0267907; EP 1 250 365; WO 97/9740075; WO 03/045551; WO 02/002576; US 2015/0025205; U.S. Ser. No. 14/572,195; filed Dec. 16, 2014; U.S. Pat. No. 9,193,856; WO 2004/052945; US 2016/0032025; and Journal of Molecular Catalysis A: Chemical (20010705), 172(1-2), pp. 43-65.
This invention relates to co-owned U.S. Pat. No. 9,249,239 and co-pending applications U.S. Ser. No. 15/000,731, filed Jan. 19, 2016; U.S. Ser. No. 14/324,333, filed Jul. 7, 2014; U.S. Ser. No. 14/324,408, filed Jul. 7, 2014; and U.S. Ser. No. 14/324,427, filed Jul. 7, 2014.
There is still a need in the art for new and improved catalyst systems for the polymerization of olefins, in order to achieve specific polymer properties, such as high melting point, high molecular weights, to increase conversion or comonomer incorporation, or to alter comonomer distribution without deteriorating the resulting polymer's properties.
It is therefore an object of the present invention to provide novel catalyst compounds, catalysts systems comprising such compounds, and processes for the polymerization of olefins using such compounds and systems.
Furthermore, it is an objective of the present invention to provide olefin polymers, particularly propylene homopolymers, and random copolymers of propylene with ethylene and/or higher alpha-olefins.